Method of making stems for sealed electrical devices



A. J. WHITE El AL 2,153,404

OF MAKING STEMS FOR SEALED ELECTRICAL DEVICES April 4, 1939.

METHOD Filed April 19, 1954 fNI ENT DR 5' ARTHUR W H175 FER 5 Y JJ HNSUN THEIR ATTURNE Y' Patented Apr. 4, 1939 UNITED STATES mn'rnon or MAKING STEMS non SEALED ELECTRICAL DEVICES Arthur J. White, Cleveland Heights, and Percy J. Johnson,8haker Heights, Ohio, assignors to General Electric Company, a corporation of New York Application April 19, 1934, Serial No. 121,270.

Claims.

Our invention relates to so-called tipless radio tubes, incandescent lamps and similar devices and to methods of manufacturing the same.

The present practice in making the stems 5 which carry the exhaust tube and the leadingin wires upon which the internal elements of the radio tubes or incandescent lamps are mounted, is to assemble a stem tube, anexhaust tube and the leading-in wires with the inner ends of 10. the stem and exhaust tubes substantially in line.

The expression "inner end is used herein with reference to the stem to indicate that end of the said tube which extends into the bulb and in which the leading-in wires are sealed, while the expression outer end indicates the end which is united to the bulb. The corresponding ends of the exhaust tube are similarly designated.

' The said inner ends of the exhaust and stem tubes are fused together and then compressed by clamping the fused glass around the lead wires. This results in a "press portion consisting of a flat solid mass of glass at the inner end of the stem tube with the leading-in wires extending therethrough and disposed side by side in a line. Air pressure is then applied through the exhaust tube, and additional heat may be supplied to thoroughly fuse the glass around the inner end of the exhaust tube, thus causing the mass of glass to swell and become bulb shaped. As the air pressure is continued, .a passage is blown through the glass at an angle to the flat surface of the press portion. The exhaust tube communicates through this passage with the interior of the bulb when the stem is sealed there-f 5 to. This process is disclosed in Patent No.

' 1,423,956, Mitchell and White.

The above described type of stem has the disadvantage that the linearly disposed leading-in be'comparatively,large and therefore necessi-.

tates the use:of a large bulb. It is desirable :in

445 many cases to usea smaller bulb, as in tubes for radio sets for automobiles, where compactness is According to our invention, the exhaust tube is closed at its inner end and it is preterable to blow a small bulb at this end, although this is not essential. 'l'he parts are then assembled with the bulbous end of the exhaust tube subv stantial'ly in line with the inner end of the stem tube and the leading-in wires dis'posed'in spaced.

relationship between the said ends of the steni and exhaust tubes. Any number of leading-in wires may be arranged in any desired relationship, for example, in a circle, square, oblong or triangle. The application of a flame results in a fusing together of the inner ends of the stem and exhaust tubes and the introduction of air pressure into the outer end of the exhaust tube prevents the walls of the tubes from collapsing and fusing solidly, thus forming a chamber or bulb portion having the leading-in wires sealed in the walls thereof without the application of external pressure. As the air pressure is continued, a passage or aperture is formed for communication of the exhaust tube with the interior of the bulb when the stem is sealed thereto. The said passage may be formed at the side or at the end of the stem, depending upon which is the hotter, and this of course may be controlled.

Among the advantages of the type of stem comprising our invention are: Greater spacing of leading-in wires for a given diameter of stem tube; the use of a smaller stem tube, which permits the use of a smaller bulb or enclosure; and the arrangement of any number of leads as required. An annular or circular arrangement of leading-in wires is particularly suitable for radio tubes, inakingpossible the use of a large number oi wires, suitably spaced apart and providing a compact and rigid supporting structure for the internal elements of the said tubes. The invention is of course also applicable to incandescent lamps, particularly to multiple filament lamps which employ a number of lead wires.

Further features and advantages of our invention will appear from the following detailed description of species thereof and from the drawing. I

In the drawing, Fig. 1 is an elevation in section showing the way in which the parts of the stem are preliminarily assembled according to our invention; Fig. 2 is a similar view showingthe stem tube and exhaust tube fused together, both views corresponding to a section through 2-2 of Fig.4; Fig. 3 is an elevation in section of a finished stem having a transverse aperture or passage through which the exhaust tube communicates with the interior of the bulb, the section being taken at 3-3 ofFig. 4; Fig. 4 is a plan view of the stem shown in Figs. l3; Fig. 5 is I an elevation in section showing a method of makof an incandescentfiamp having a stem compris-v view of a radio tube having a stem comprising our invention; and Fig. 9 is a perspective view ing our invention.

Referring to Fig. 1, the first stepin making a V until the end of said bulb comes to rest on the block II. The parts are then disposed as shown in the drawing with portions of the leading-in wires between the innerend of the stem tube'and the bulb end of the exhaust tube.

Referring to Fig. 2, the application of a flame or flames l1 results in a fusing together of the end of the stem tube i4 and the bulb IQ. As seen in Fig. 2, the wall of the bulbous portion l6 and the wall of the inner end of the stem tube I4 are sealed around their entire peripheries to enclose portions of the leading-in wires Hi therebetween. Air pressure is then, introduced into the exhaust tube l5 from a nozzle II to prevent and-an exhaust passage 33 with the interim;

the walls of the tubes from collapsing and form ing a solid mass of glass, the ends of the stem and exhaust tubes merging instead to form a chamber or bulb-shaped portion ll having portions of the leading-in wires i sealed in the walls bulb when the stem is sealed thereto. Air pressure is then introduced between the stem tube It and exhaust tube It from a nozzle I 8' to round out the joint at 20' between said stem and exhaust tubes to prevent cracking. The said aperture is may be formed at the side or at the end of the stem depending upon which is the hotter,

. tube It results in the formation of a passage or and this of course may be controlled. For example, when an aperture at the end is desired, it may be accomplished as shown in Fig. ,5, by raising the stem so that there is a space between the end thereof and the block l2, and directing the flames i1 into said space. This causes the said end of the stem to be heated intensively so that the application of air pressure into the exhaust aperture 20 at the said end. The formation of a. passage atthe side, as at I! in Fig. 3, always occurs between a pair of leading-in wires since the said wires conduct the heat away rapidly. and the seal between the said wires and the glass is therefore not interfered with.

Fig. 4 shows the annular distribution of six leading-in wires i0 as made according to Figs. 1-3. The number and arrangement of lead wires may of course be varied as required. They may be disposed, for example, or triangle.

Instead of an exhaust tube having a bulb at one end such as that used in l ig 1, w symmetrical tube} I, as shown in Fig. 6, maybe employed, the said tube 2i being closed off at one end 22. The procedure is the same as that described in connection with Figs. 1-8

in a circle, square, oblong shown in Fig. 'l, the exhaust passage being illustrated at 23.

A radio tube having a stem ll of the type shown in Figs. 3-4 is illustrated inj'ig. 8, the exhaust passage being illustrated at 24. A flare 25 at the outer end of the stem is sealed to the end of the bulb 28 which is evacuated through the exhaust tube l which is then sealed-01f at 21. The internal elements 28 characteristic of this type of device are mounted on the support and leading-in wires ill, the annular arrangement of the wires as'shown making possible a very rigid and compact assembly of the said internal elements. The use of a comparatively small bulb is made possible by the annular disposition of the leading-in and supporting wires instead of a linear disposition in which the leads pass through a flat stem press. In order to get the proper spacing between the leads with the flat stem press used heretofore, the

said press had to be made comparatively wide, and

of the bulb. The particular lamp illustrated employs three leading-in wires 34, 35, 36, which are .triangularly disposed and portions of which are sealed in the walls of the correspondingly substantially triangular shaped chamber 32' at the inner end of the stem 29. A filament 31 is mounted on the leading-in wires 34, 35, and a second'fllament 38 is mounted on the leading-in wire 36 and on a branch lead 39 which is mounted on the common lead 35.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of making stems for sealed electrical devices which consists in assembling a stem tube, an exhaust tube inside of said stem tube and closed at one end and leading-in wires extending longitudinally between said tubes, fusing together portions of the walls of said stem tube and exhaust tube around their entire'peripheries to enclose portions of said leading-in wires therein, the entire fused portions of said stem and exhaust tubes forming the side walls of a chamber and the closed end of the exhaust tube forming the end wall of said chamber, and delivering air pressure into said exhaust tube to prevent the.

said walls of the chamber from collapsing and to blow an aperture through a portion of said chamber. r

2. The methodof making stems for sealed electrical devices which consists in assembling a stem tube. an exhaust tube inside of said stem tube and having a bulb portion at one end and leading-in wires extending longitudinally between said stem tube and the bulb portion of said exhaust tube,- fusing together portions of theWalls of said stem tube and bulb portion of said exhaust tube around their entireperipheries to and theclosed endof the exhaust tube formingthe end wall of'said chamber, and delivering air pressure into said exhaust tube to prevent the said and results in the stem walls of the chamber from collapsing to I .J blow-an aperture through the wall of said chamber.

3. The method 01' making stems for sealed electrical deviceswhich consists in assembling a stem tube, an exhaust tube inside of said stem tube and closed at one end and leading-in wires extending longitudinally between said tubes, applying heat to portions of the walls of said tubes to fuse together said portions of the walls oi said stem tube and exhaust tube around their entire peripheries to enclose portions of said leading-in wires therein, the entire fused portions oi said stem and exhaust tubes forming the side walls of a chamber and the closed end of the exhaust tube forming the end. wall of said chamber, and

- delivering air pressure into said exhaust tube to prevent the said walls of the chamber from col-v lapsing and to blow a transverse aperture through the wall of said chamber. I

4. The method of makingstems for sealed electrical devices which consists in assembling a stem tube, an exhausttube-inside 01 said stem tube and closed at its inner end and a plurality of leading-in wires extending longitudinally. be-

tween said tubes, said leading-in wires being supported in spaced relationship in openings in a block andcsaid stem and exhaust tubes being disposed with their inner ends on said block, fusing together portions of the walls of said stem tube,

and said exhaust tube around their entire pecol1apsing aid to blow an aperture ripheries to ot-said leading-in wires therein, the entire i'usedportions 0! said stem and exhaust tubes forming the sidewalls of a chamber and the closed end of the exhaust tube forming the end wall 01' said chamber, and delivering air pressure into said exhaust tube to prevent the said walls of the chamber from col lapsing and to blow an aperture through the g of said chamber.

5. The method of making stems for sealed electrical devices which consists in assembling a. stem tube, an exhaust tube inside or said stem tube and closed at one end, the closed end of said exhaust tube being located adjacent to one end of said stem tube, and leading-in wires extending longitudinally between said tubes and held rigidly in s walls of thesaid adjacent end portions of said stem tube and exhaust tube around their entireperipheries to enclose portions oi said leading-in wires therebetween, the entire fused portions of ced reiationshimiusing together-the said stem and exhaust tubes forming the side walls of a chamber and the closed end of the ex-' 

